diff options
| -rw-r--r-- | name-hash.c | 492 |
1 files changed, 485 insertions, 7 deletions
diff --git a/name-hash.c b/name-hash.c index 3f7722a63b..cac313c78d 100644 --- a/name-hash.c +++ b/name-hash.c @@ -23,15 +23,21 @@ static int dir_entry_cmp(const struct dir_entry *e1, name ? name : e2->name, e1->namelen); } -static struct dir_entry *find_dir_entry(struct index_state *istate, - const char *name, unsigned int namelen) +static struct dir_entry *find_dir_entry__hash(struct index_state *istate, + const char *name, unsigned int namelen, unsigned int hash) { struct dir_entry key; - hashmap_entry_init(&key, memihash(name, namelen)); + hashmap_entry_init(&key, hash); key.namelen = namelen; return hashmap_get(&istate->dir_hash, &key, name); } +static struct dir_entry *find_dir_entry(struct index_state *istate, + const char *name, unsigned int namelen) +{ + return find_dir_entry__hash(istate, name, namelen, memihash(name, namelen)); +} + static struct dir_entry *hash_dir_entry(struct index_state *istate, struct cache_entry *ce, int namelen) { @@ -112,21 +118,493 @@ static int cache_entry_cmp(const struct cache_entry *ce1, return remove ? !(ce1 == ce2) : 0; } -static void lazy_init_name_hash(struct index_state *istate) +static int lazy_try_threaded = 1; +static int lazy_nr_dir_threads; + +#ifdef NO_PTHREADS + +static inline int lookup_lazy_params(struct index_state *istate) { - int nr; + return 0; +} + +static inline void threaded_lazy_init_name_hash( + struct index_state *istate) +{ +} + +#else + +#include "thread-utils.h" + +/* + * Set a minimum number of cache_entries that we will handle per + * thread and use that to decide how many threads to run (upto + * the number on the system). + * + * For guidance setting the lower per-thread bound, see: + * t/helper/test-lazy-init-name-hash --analyze + */ +#define LAZY_THREAD_COST (2000) + +/* + * We use n mutexes to guard n partitions of the "istate->dir_hash" + * hashtable. Since "find" and "insert" operations will hash to a + * particular bucket and modify/search a single chain, we can say + * that "all chains mod n" are guarded by the same mutex -- rather + * than having a single mutex to guard the entire table. (This does + * require that we disable "rehashing" on the hashtable.) + * + * So, a larger value here decreases the probability of a collision + * and the time that each thread must wait for the mutex. + */ +#define LAZY_MAX_MUTEX (32) + +static pthread_mutex_t *lazy_dir_mutex_array; + +/* + * An array of lazy_entry items is used by the n threads in + * the directory parse (first) phase to (lock-free) store the + * intermediate results. These values are then referenced by + * the 2 threads in the second phase. + */ +struct lazy_entry { + struct dir_entry *dir; + unsigned int hash_dir; + unsigned int hash_name; +}; + +/* + * Decide if we want to use threads (if available) to load + * the hash tables. We set "lazy_nr_dir_threads" to zero when + * it is not worth it. + */ +static int lookup_lazy_params(struct index_state *istate) +{ + int nr_cpus; + + lazy_nr_dir_threads = 0; + + if (!lazy_try_threaded) + return 0; + + /* + * If we are respecting case, just use the original + * code to build the "istate->name_hash". We don't + * need the complexity here. + */ + if (!ignore_case) + return 0; + + nr_cpus = online_cpus(); + if (nr_cpus < 2) + return 0; + + if (istate->cache_nr < 2 * LAZY_THREAD_COST) + return 0; + + if (istate->cache_nr < nr_cpus * LAZY_THREAD_COST) + nr_cpus = istate->cache_nr / LAZY_THREAD_COST; + lazy_nr_dir_threads = nr_cpus; + return lazy_nr_dir_threads; +} + +/* + * Initialize n mutexes for use when searching and inserting + * into "istate->dir_hash". All "dir" threads are trying + * to insert partial pathnames into the hash as they iterate + * over their portions of the index, so lock contention is + * high. + * + * However, the hashmap is going to put items into bucket + * chains based on their hash values. Use that to create n + * mutexes and lock on mutex[bucket(hash) % n]. This will + * decrease the collision rate by (hopefully) by a factor of n. + */ +static void init_dir_mutex(void) +{ + int j; + + lazy_dir_mutex_array = xcalloc(LAZY_MAX_MUTEX, sizeof(pthread_mutex_t)); + + for (j = 0; j < LAZY_MAX_MUTEX; j++) + init_recursive_mutex(&lazy_dir_mutex_array[j]); +} + +static void cleanup_dir_mutex(void) +{ + int j; + + for (j = 0; j < LAZY_MAX_MUTEX; j++) + pthread_mutex_destroy(&lazy_dir_mutex_array[j]); + + free(lazy_dir_mutex_array); +} + +static void lock_dir_mutex(int j) +{ + pthread_mutex_lock(&lazy_dir_mutex_array[j]); +} + +static void unlock_dir_mutex(int j) +{ + pthread_mutex_unlock(&lazy_dir_mutex_array[j]); +} + +static inline int compute_dir_lock_nr( + const struct hashmap *map, + unsigned int hash) +{ + return hashmap_bucket(map, hash) % LAZY_MAX_MUTEX; +} + +static struct dir_entry *hash_dir_entry_with_parent_and_prefix( + struct index_state *istate, + struct dir_entry *parent, + struct strbuf *prefix) +{ + struct dir_entry *dir; + unsigned int hash; + int lock_nr; + + /* + * Either we have a parent directory and path with slash(es) + * or the directory is an immediate child of the root directory. + */ + assert((parent != NULL) ^ (strchr(prefix->buf, '/') == NULL)); + + if (parent) + hash = memihash_cont(parent->ent.hash, + prefix->buf + parent->namelen, + prefix->len - parent->namelen); + else + hash = memihash(prefix->buf, prefix->len); + + lock_nr = compute_dir_lock_nr(&istate->dir_hash, hash); + lock_dir_mutex(lock_nr); + + dir = find_dir_entry__hash(istate, prefix->buf, prefix->len, hash); + if (!dir) { + FLEX_ALLOC_MEM(dir, name, prefix->buf, prefix->len); + hashmap_entry_init(dir, hash); + dir->namelen = prefix->len; + dir->parent = parent; + hashmap_add(&istate->dir_hash, dir); + + if (parent) { + unlock_dir_mutex(lock_nr); + + /* All I really need here is an InterlockedIncrement(&(parent->nr)) */ + lock_nr = compute_dir_lock_nr(&istate->dir_hash, parent->ent.hash); + lock_dir_mutex(lock_nr); + parent->nr++; + } + } + unlock_dir_mutex(lock_nr); + + return dir; +} + +/* + * handle_range_1() and handle_range_dir() are derived from + * clear_ce_flags_1() and clear_ce_flags_dir() in unpack-trees.c + * and handle the iteration over the entire array of index entries. + * They use recursion for adjacent entries in the same parent + * directory. + */ +static int handle_range_1( + struct index_state *istate, + int k_start, + int k_end, + struct dir_entry *parent, + struct strbuf *prefix, + struct lazy_entry *lazy_entries); + +static int handle_range_dir( + struct index_state *istate, + int k_start, + int k_end, + struct dir_entry *parent, + struct strbuf *prefix, + struct lazy_entry *lazy_entries, + struct dir_entry **dir_new_out) +{ + int rc, k; + int input_prefix_len = prefix->len; + struct dir_entry *dir_new; + + dir_new = hash_dir_entry_with_parent_and_prefix(istate, parent, prefix); + + strbuf_addch(prefix, '/'); + + /* + * Scan forward in the index array for index entries having the same + * path prefix (that are also in this directory). + */ + if (strncmp(istate->cache[k_start + 1]->name, prefix->buf, prefix->len) > 0) + k = k_start + 1; + else if (strncmp(istate->cache[k_end - 1]->name, prefix->buf, prefix->len) == 0) + k = k_end; + else { + int begin = k_start; + int end = k_end; + while (begin < end) { + int mid = (begin + end) >> 1; + int cmp = strncmp(istate->cache[mid]->name, prefix->buf, prefix->len); + if (cmp == 0) /* mid has same prefix; look in second part */ + begin = mid + 1; + else if (cmp > 0) /* mid is past group; look in first part */ + end = mid; + else + die("cache entry out of order"); + } + k = begin; + } + + /* + * Recurse and process what we can of this subset [k_start, k). + */ + rc = handle_range_1(istate, k_start, k, dir_new, prefix, lazy_entries); + + strbuf_setlen(prefix, input_prefix_len); + + *dir_new_out = dir_new; + return rc; +} + +static int handle_range_1( + struct index_state *istate, + int k_start, + int k_end, + struct dir_entry *parent, + struct strbuf *prefix, + struct lazy_entry *lazy_entries) +{ + int input_prefix_len = prefix->len; + int k = k_start; + + while (k < k_end) { + struct cache_entry *ce_k = istate->cache[k]; + const char *name, *slash; + + if (prefix->len && strncmp(ce_k->name, prefix->buf, prefix->len)) + break; + + name = ce_k->name + prefix->len; + slash = strchr(name, '/'); + + if (slash) { + int len = slash - name; + int processed; + struct dir_entry *dir_new; + + strbuf_add(prefix, name, len); + processed = handle_range_dir(istate, k, k_end, parent, prefix, lazy_entries, &dir_new); + if (processed) { + k += processed; + strbuf_setlen(prefix, input_prefix_len); + continue; + } + + strbuf_addch(prefix, '/'); + processed = handle_range_1(istate, k, k_end, dir_new, prefix, lazy_entries); + k += processed; + strbuf_setlen(prefix, input_prefix_len); + continue; + } + + /* + * It is too expensive to take a lock to insert "ce_k" + * into "istate->name_hash" and increment the ref-count + * on the "parent" dir. So we defer actually updating + * permanent data structures until phase 2 (where we + * can change the locking requirements) and simply + * accumulate our current results into the lazy_entries + * data array). + * + * We do not need to lock the lazy_entries array because + * we have exclusive access to the cells in the range + * [k_start,k_end) that this thread was given. + */ + lazy_entries[k].dir = parent; + if (parent) { + lazy_entries[k].hash_name = memihash_cont( + parent->ent.hash, + ce_k->name + parent->namelen, + ce_namelen(ce_k) - parent->namelen); + lazy_entries[k].hash_dir = parent->ent.hash; + } else { + lazy_entries[k].hash_name = memihash(ce_k->name, ce_namelen(ce_k)); + } + + k++; + } + + return k - k_start; +} + +struct lazy_dir_thread_data { + pthread_t pthread; + struct index_state *istate; + struct lazy_entry *lazy_entries; + int k_start; + int k_end; +}; + +static void *lazy_dir_thread_proc(void *_data) +{ + struct lazy_dir_thread_data *d = _data; + struct strbuf prefix = STRBUF_INIT; + handle_range_1(d->istate, d->k_start, d->k_end, NULL, &prefix, d->lazy_entries); + strbuf_release(&prefix); + return NULL; +} + +struct lazy_name_thread_data { + pthread_t pthread; + struct index_state *istate; + struct lazy_entry *lazy_entries; +}; + +static void *lazy_name_thread_proc(void *_data) +{ + struct lazy_name_thread_data *d = _data; + int k; + + for (k = 0; k < d->istate->cache_nr; k++) { + struct cache_entry *ce_k = d->istate->cache[k]; + ce_k->ce_flags |= CE_HASHED; + hashmap_entry_init(ce_k, d->lazy_entries[k].hash_name); + hashmap_add(&d->istate->name_hash, ce_k); + } + + return NULL; +} + +static inline void lazy_update_dir_ref_counts( + struct index_state *istate, + struct lazy_entry *lazy_entries) +{ + int k; + + for (k = 0; k < istate->cache_nr; k++) { + if (lazy_entries[k].dir) + lazy_entries[k].dir->nr++; + } +} + +static void threaded_lazy_init_name_hash( + struct index_state *istate) +{ + int nr_each; + int k_start; + int t; + struct lazy_entry *lazy_entries; + struct lazy_dir_thread_data *td_dir; + struct lazy_name_thread_data *td_name; + + k_start = 0; + nr_each = DIV_ROUND_UP(istate->cache_nr, lazy_nr_dir_threads); + + lazy_entries = xcalloc(istate->cache_nr, sizeof(struct lazy_entry)); + td_dir = xcalloc(lazy_nr_dir_threads, sizeof(struct lazy_dir_thread_data)); + td_name = xcalloc(1, sizeof(struct lazy_name_thread_data)); + + init_dir_mutex(); + + /* + * Phase 1: + * Build "istate->dir_hash" using n "dir" threads (and a read-only index). + */ + for (t = 0; t < lazy_nr_dir_threads; t++) { + struct lazy_dir_thread_data *td_dir_t = td_dir + t; + td_dir_t->istate = istate; + td_dir_t->lazy_entries = lazy_entries; + td_dir_t->k_start = k_start; + k_start += nr_each; + if (k_start > istate->cache_nr) + k_start = istate->cache_nr; + td_dir_t->k_end = k_start; + if (pthread_create(&td_dir_t->pthread, NULL, lazy_dir_thread_proc, td_dir_t)) + die("unable to create lazy_dir_thread"); + } + for (t = 0; t < lazy_nr_dir_threads; t++) { + struct lazy_dir_thread_data *td_dir_t = td_dir + t; + if (pthread_join(td_dir_t->pthread, NULL)) + die("unable to join lazy_dir_thread"); + } + + /* + * Phase 2: + * Iterate over all index entries and add them to the "istate->name_hash" + * using a single "name" background thread. + * (Testing showed it wasn't worth running more than 1 thread for this.) + * + * Meanwhile, finish updating the parent directory ref-counts for each + * index entry using the current thread. (This step is very fast and + * doesn't need threading.) + */ + td_name->istate = istate; + td_name->lazy_entries = lazy_entries; + if (pthread_create(&td_name->pthread, NULL, lazy_name_thread_proc, td_name)) + die("unable to create lazy_name_thread"); + + lazy_update_dir_ref_counts(istate, lazy_entries); + + if (pthread_join(td_name->pthread, NULL)) + die("unable to join lazy_name_thread"); + + cleanup_dir_mutex(); + + free(td_name); + free(td_dir); + free(lazy_entries); +} + +#endif + +static void lazy_init_name_hash(struct index_state *istate) +{ if (istate->name_hash_initialized) return; hashmap_init(&istate->name_hash, (hashmap_cmp_fn) cache_entry_cmp, istate->cache_nr); hashmap_init(&istate->dir_hash, (hashmap_cmp_fn) dir_entry_cmp, istate->cache_nr); - for (nr = 0; nr < istate->cache_nr; nr++) - hash_index_entry(istate, istate->cache[nr]); + + if (lookup_lazy_params(istate)) { + hashmap_disallow_rehash(&istate->dir_hash, 1); + threaded_lazy_init_name_hash(istate); + hashmap_disallow_rehash(&istate->dir_hash, 0); + } else { + int nr; + for (nr = 0; nr < istate->cache_nr; nr++) + hash_index_entry(istate, istate->cache[nr]); + } + istate->name_hash_initialized = 1; } +/* + * A test routine for t/helper/ sources. + * + * Returns the number of threads used or 0 when + * the non-threaded code path was used. + * + * Requesting threading WILL NOT override guards + * in lookup_lazy_params(). + */ +int test_lazy_init_name_hash(struct index_state *istate, int try_threaded) +{ + lazy_nr_dir_threads = 0; + lazy_try_threaded = try_threaded; + + lazy_init_name_hash(istate); + + return lazy_nr_dir_threads; +} + void add_name_hash(struct index_state *istate, struct cache_entry *ce) { if (istate->name_hash_initialized) |